108 MR. H. WILDE ON A PROPERTY OF 



in order to produce synchronous rotation^ it was not at all 

 essential that the circuit which conveyed the combined 

 currents for producing the light should be completed, 

 provided that the ends of the coils of each armature were 

 connected respectively with the same metal plates which 

 formed the polar terminals of the machines. In this case 

 the armatures adjusted themselves to their normal posi- 

 tions even more readily than when the current was produ- 

 cing the light. The accompanyiug diagram will assist 

 in explaining these observations more fully. 



-o F o- 



-o H t>- 



Let D and D represent the two armature-coils^ which, 

 though each 280 feet long, may virtually be represented 

 by a single turn ; EE the two outer extremities of the 

 coils, both connected by means of the metal rings and 

 brushes with the metal terminal plate E ; GG the inner 

 extremities of the same coils, similarly connected with the 

 terminal plate H. The synchronous rotation of the 

 armatures and coils D and D, as I have said, occurs either 

 when the light is produced by the combined currents 

 transmitted from the polar terminals F and H, or when 

 the circuit which conveyed these combined currents is 

 broken. 



The synchronism, however, is no longer preserved when 

 a short circuit is made between the terminals F and H by 

 substituting a good conductor for the carbon points, or 

 for the long piece of iron wire which was fused. Nor, 

 again, was the synchronism preserved when contact be- 

 tween the metal plate H and one of the ends (G) of the 

 coil was broken. In the latter case it was observed that. 



